Tory leader Michael Howard supports a reduction in the legal limit when abortions are allowed from 24 weeks to 20 and has said current rules are "tantamount to abortion on demand".

But Prime Minister Tony Blair has made it clear he has no plans to change the law.

He says abortion should not be an election issue, arguing it is a matter for individual conscience.

Liberal Democrat leader Charles Kennedy said he had previously voted for a 22-week limit but medical advances mean "I don't know what I would do now".

'Deliberate termination'

Dr Williams said the large majority of Christians considered abortion "the deliberate termination of a human life".

The current law had created a "groundswell of distaste" in the country at large, he said.

Dr Williams said technological advances had provided a clearer picture of foetuses' consciousness and sensitivity to pain, and helped to keep prematurely-born babies alive.

That had prompted "a sharper recognition of the foetus as a natural candidate for 'rights' of some kind", he said.

Dr Williams said raising the issue with parliamentary candidates - though unlikely to lead to any electoral pledges - could help to open up a necessary public debate.

"It would be a real failure if agreeing that it was not an electoral issue provided an alibi for taking it seriously as a public issue," he wrote.

Dr Williams insisted that Christians must be allowed to take part in that debate.

He said the idea that it entailed capitulating to what he called "a Neanderthal Christian Right that was plotting a takeover" was alarmist nonsense.

Meanwhile, a poll of 800 adults commissioned by the Sunday Express found that 60% of respondents said the time limit for abortions should be cut.

Some 24% backed the present limit and 76% of those interviewed by NOP World said the limit should not be any different for under 16s.

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